In contrast to the public health achievement of reducing overall US smoking rates from >50 percent in the 1960s to ~20 percent by 2000, the rate of smoking among those with serious mental illness (SMI) remains 2-3 times greater than in the general population. Recent data has shown that any small decline in smoking rates occurring in the general population in the past decade has not been seen among smokers with an SMI. In fact, 44 percent of all the cigarettes consumed in the US are by individuals with a psychiatric disorder and the number one cause of death among Americans with a psychiatric disorder is a tobacco-related disease. Unfortunately, < 25 percent of smokers with SMI receive evidence-based treatment for their tobacco use disorder (TUD). Transforming the public mental healthcare infrastructure to adhere to guidelines for the provision of evidence-based TUD treatment is an NIMH priority and is part of a national effort to meet Healthy People 2020 target goals for tobacco use. Current FDA-approved medications for TUD and guideline-based behavioral smoking cessation treatments are safe and efficacious for smokers with SMI and public mental healthcare facilities are ideal settings for integrating TUD treatments. Yet, systemic (e.g., lack of training) and cultural (e.g., belief that smoking cessation will cause decompensation) barriers within the mental healthcare system are preventing smokers with SMI from receiving evidence-based TUD treatment. Facilitating the adoption and sustainability of evidence-based practice for TUD within public mental healthcare clinics requires an organization-level intervention to address barriers that hinder effective care. Preliminary studies by members of the research team in community mental healthcare settings have shown that an organization-level intervention reduces barriers to providing evidence-based TUD treatment and improves clinician adherence to treatment guidelines. Thus, with a cluster-randomized design and 16 community mental healthcare agencies (N=320 personnel, N=800 clients), this study will evaluate the Addressing Tobacco Through Organizational Change (ATTOC) model for: 1) improving provider adherence to guidelines for treating TUD; and 2) reducing client smoking rates, vs. usual care (UC). Non-inferiority testing will determine if the ATTOC model adversely affects client mental health functioning, vs. UC, and the cost-effectiveness of the ATTOC intervention will be assessed. We will also explore changes in barriers as mediators of the effects of the ATTOC model on provider adherence to treatment guidelines and patient smoking and identify key ATTOC components linked to improved outcomes that can be more easily disseminated. If this trial shows that ATTOC can promote evidence-based care for TUD and reduce smoking rates for those with an SMI - and without worsening mental health and in a cost- effective manner - this organizational change model may represent a critical initiative to address tobacco use in an under-served sub-group of smokers and help to attain Healthy People 2020 tobacco use goals.